1. Field of the Invention
The invention relates to a video display method and a video display apparatus which can emphasize a stereoscopic feeling in a video signal.
2. Description of the Related Art
Among stereoscopic display systems, there is a stereoscopic display system using a right/left parallax information as a system having the highest possibility of realization. According to this system, two cameras are used upon photographing and a signal for the left eye and a signal for the right eye are obtained. Upon reception, the right-eye signal and left-eye signal are reproduced so as to be displayed to each eye.
FIG. 1 shows a principle of the stereoscopic observing operation using the binocular (right/left) parallax. Images obtained by shifting a left-eye video image 3L and a right-eye video image 3R in the horizontal direction are displayed on a display surface 1. Usually, a focal point of both of left and right eyes (2L, 2R) (it is an intersecting point where the right and left sight lines cross and is called a point where vergence is matched) and a focal point of each eye (2L, 2R) (it is a point where an adjustment of the single eye is matched) are the same location. Specifically speaking, a CRT surface in case of a CRT or the like is a location where the vergence and the adjustment are matched. A screen in case of a projector or the like is a location where the vergence and the adjustment are matched.
FIG. 1A shows a case of a cross vergence. In this case, the video image 3R shifted to the left is displayed to the right eye 2R and the video image 3L shifted to the right is displayed to the left eye 2L. At this time, an image is fused in the head as if an object existed at the position where the vergences of the right and left eyes are matched. A virtual image 4A is seen as if it was projected toward this side from the display surface 1. FIG. 1B shows a case of a parallel vergence (non-cross vergence). In this case, the video image 3L shifted to the left is displayed to the left eye 2L and the video image 3R shifted to the right is displayed to the right eye 2R. In the parallel vergence, a virtual image 4B is fused behind the display surface 1.
A process to obtain a stereoscopic feeling by using such a principle of the binocular parallax even in an ordinary 2-dimensional image is an emphasis of a stereoscopic feeling using an effect of a Pulfrich.
The Pulfrich's effect (or Pulfrich's law) is a principle such that "when an object which reciprocates to the right and left in a vertical plane in front of the eyes is observed by the both eyes while a filter (ND filter) to reduce the light is attached to one of the eyes, the object is seen as if it moved while drawing an elliptic locus with a depth in a manner such that the object is located in front of and behind the inside of the vertical plane". For example, as shown in FIG. 2, if a pendulum which reciprocates to the right and left in a plane 6 is seen in a state where an ND filter 5 is attached to the left eye 2L, the pendulum is observed in a manner such that when the pendulum moves from the right to the left, the pendulum passes in front of the plane 6 and, when the pendulum moves from the left to the right, the pendulum passes behind the plane 6 and the locus of the pendulum forms an elliptic orbit 7.
Such a Pulfrich's effect occurs because, when signals from the eyes is transmitted to the cerebrum, a time that is required until the signal is transmitted from the left eye 2L to which the light was weakened to the cerebrum has a time delay as compared with that from the right eye 2R to which the light is not weakened. That is, in the example of FIG. 2, when the pendulum moves from the right to the left and exists at a position of q, the signal from the left eye 2L is delayed, so that the left eye 2L recognizes the pendulum as if it existed at a position of p at this moment. A binocular parallax occurs as mentioned above and the viewer feels as if the pendulum existed at a position of N due to the cross vergence shown in FIG. 1A mentioned above. On the contrary, when the pendulum moves from the left to the right and exists at the position of q, the left eye 2L recognizes the pendulum as if it existed at a position of r. Due to the binocular parallax, the viewer feels as if the pendulum existed at a position of F due to the parallel vergence shown in FIG. 1B.
As mentioned above, there is the method using the Pulfrich's effect as a method of emphasizing the stereoscopic feeling of an ordinary 2-dimensional video image.
The Pulfrich's effect, however, has drawbacks such that only a moving object can be stereoscopically seen and the stereoscopic feeling is influenced by a moving speed and a moving direction, namely, a depth feeling changes depending on the moving speed and there is a problem such that the front side and the rear side are unconditionally determined by the moving direction.
That is, there is a problem such that the Pulfrich's effect does not function for a still image although a stereoscopic feeling (depth feeling) of only an object which moves in a specific direction is merely enhanced.